Experimental investigation on the flow patterns in a T-junction under steady and rolling motion conditions using PLIF.

• A new classification criterion of flow pattern in the T-junction under steady condition is proposed. • The rolling motion causes the branch jet to sweep up and down in the T-junction. • The influence map on the sweeping phenomenon under rolling motion condition is proposed. Flow mixing experiments are performed on the Ocean Conditions Simulation Platform (OCSP) test facility to investigate the flow pattern evolution mechanisms in a T-junction with branch jet under steady and rolling motion conditions. Plane Laser-Induced Fluorescence (PLIF) technology is used to display and test the instantaneous flow pattern in the T-junction. The effects of the main fluid Reynolds number, inflow rate ratio and rolling Reynolds number on the flow pattern characteristics are discussed at a range of 2110–15850, 1–20 and 0–3520, respectively. Based on the experimental results, new classification criteria of flow pattern in the T-junction under steady condition are proposed from the perspective of the evolution of vortex structure. The flow patterns are classified into the single shear vortex, co-rotating vortex pair, transition region and counter-rotating vortex pair according to the fluid Reynolds number and inflow rate ratio. Under rolling motion condition, the branch jet periodically sweeps up and down in the T-junction due to the effect of additional inertial force. The sweeping phenomenon of the branch jet caused by rolling motion enhances the flow instability in the T-junction that can be inhibited by increasing the fluid Reynolds number or decreasing the inflow rate ratio and rolling Reynolds number. In addition, the influence mechanisms of fluid Reynolds number, inflow rate ratio and rolling Reynolds number on the flow pattern in the T-junction are investigated. These results can inform the analysis, design, safe operation and performance improvement of equipment in various industrial applications involving flow mixing in a T-junction. [ABSTRACT FROM AUTHOR]